In the field of rubber stamps, it is now well known that stamp pads may be fabricated from a pre-inked rubber material. These pre-inked stamps may be used in lieu of conventional stamps which must first be inked, such as by stamping them on an ink pad, before duplicating an image on a selected object.
Typically, pre-inked stamps are manufactured using several steps. First, the image to be duplicated by the stamp is prepared using a selected computer software program, typesetting, or other selected method. After the art is camera-ready, a photograph is taken and a negative is made. The negative is then placed over a photopolymer plate, after which an ultraviolet light is impinged upon the negative. The ultraviolet light serves to cure the polymer. Any uncured resin is washed away in a washout unit.
The photopolymer plate is then used to fabricate a matrix board. This process involves placing the photopolymer plate face down on the matrix board, the photopolymer plate then being driven into the board. In order to accomplish this task, the entire assembly is preheated. The matrix board is then locked into a frame designed to hold a liquid pre-inked stamp gel and pre-mix. The liquid is then heated in a press for a selected time, typically eight (8) to twenty-four (24) minutes, at a selected temperature, typically 238.degree. F. to 275.degree. F.
It is well known that the steps of preparing the artwork in camera-ready format, making the negative, making the photopolymer plate, and making the matrix board account for more than half of the materials and two-thirds of the labor used in manufacturing the pre-inked stamps. It is also well-known that these materials are typically thrown away after the particular stamp is made because they are then useless. Further, it is well known that the process of curing the photopolymer plate using ultraviolet light is both expensive and has a negative impact on the environment.
Several different methods have been developed to achieve the basic results of the above-described process of manufacturing pre-inked stamps. Typical of the art are those devices and methods disclosed in the following United States Letters Patents:
______________________________________ U.S Pat. No. Inventor(s) Issue Date ______________________________________ 3,991,145 R. M. Landsman Nov 9, 1976 3,999,918 R. M. Landsman Dec 28, 1976 4,000,243 R. A. Curren Dec 28, 1976 ______________________________________
Of these patents, the Landsman patents ('145 and '918) teach a method and apparatus, respectively, for making a printing plate from a porous substrate. The Landsman printing plate may be fabricated from polypropylene or nylon and is fabricated in much the same manner as the photopolymer plate described above.
The Curren patent ('243) describes a method for manufacturing pre-inked stamps wherein a thermoplastic material is compressed against a die, after which heat is applied thereto in order to cause the thermoplastic material to retain a memory of the die impressions. This is similar to the fabrication of the matrix board as described above.
Other methods have been developed for fabrication of various products such as rubber, wood, paper, foam, or other sheet materials. Typical of the art are those devices and methods disclosed in the following United States Letters Patents:
______________________________________ U.S Pat. No. Inventor(s) Issue Date ______________________________________ 3,679,863 P. T. Houldcroft, et al. Jul 25, 1972 3,870,852 H. Kogert Mar 11, 1975 4,002,877 C. M. Banas Jan 11, 1977 4,125,757 W. A. Ross Nov 14, 1978 4,403,134 H. Klingel Sep 6, 1983 4,740,258 H. U. Breitscheidel Apr 26, 1988 ______________________________________
Of these patents, Houldcroft, et al. ('863), teach an apparatus for cutting paper, timber, and fabric using a laser beam. A jet of air or other inert gas carrying an atomized stream of liquid coolant is directed onto the workpiece at the point at which the laser beam is concentrated in order to reduce the spread of charring or tar deposit from the cut along the surfaces of the workpiece. Houldcroft, et al., do not teach the use of similar methods in the field of rubber stamps, as the present field present problems totally unlike those in the field of cutting wood and wood products.
Kogert ('852) discloses a process and apparatus for simultaneously cutting two dissimilar materials such as rubberized wire comprising a metal wire filament having a rubberized covering.
Banas ('877) teaches a method of cutting a multi-layer pile of sheet material with a laser beam. In a fashion similar to the Houldcroft, et al. disclosure above, a stream of liquid coolant is directed toward the material at the location of the laser beam impingement, in this case in order to prevent adhesion of the adjacent layers of material, globularization, or singeing.
Ross ('757) teaches a method of cutting a thermally conductive workpiece using a laser beam wherein the workpiece is submerged into a liquid coolant. The laser beam used by Ross is a Carbon Dioxide laser beam which is described as being capable of vaporizing almost any substance known. In the present invention where a liquid ink is contained within a rubber stamp pad, it will be seen that this type of laser beam would be destructive in the manufacturing of the image upon the stamp pad.
The Klingel ('134) patent discloses a method for cutting a workpiece using a laser beam in conjunction with a stream of liquid coolant. The liquid coolant is directed at the workpiece such as to intersect the laser beam at the point of contact on the workpiece. This type of coolant system is provided in order to maintain a heat zone at a satisfactory temperature. The Klingel method is particularly intended for cutting sheet metals where a problem arises when the material evaporates, thus leaving a wide gap between the two pieces which have been cut apart from each other.
Breitscheidel ('258) teaches a method for embossing flexible sheets of foam material. The method incorporates the use of a continuous loop metallic embossing belt. This method does not teach a means for cutting or etching the rubber to the selected depth in order to create a selected pattern such as that on the face of a rubber stamp.
Although several of the prior art patents disclose methods for cutting selected materials using a laser beam while using a selected liquid coolant, none teaches a method for cutting or etching the surface of a pre-inked rubber pad such as used in stamps. The pre-inked rubber material presents problems not inherent in materials such as those described in the prior art patents such as wood, metal, and paper. Namely, the liquid ink which is contained within the pores of the rubber dissipates heat throughout the material. When a sufficient temperature is reached in order to cut the rubber, the ink has been heated beyond a degree at which it will be usable again. Therefore, even though the rubber may be cut using the methods of the prior art patents, the ink would be rendered useless.
If the gel material containing the ink is overcured, it develops plastic qualities which allow the ink to flow freely until the material is completely dry. Conversely, if the gel is undercured, it will tear apart easily.
Therefore, it is an object of this invention to provide a means for manufacturing pre-inked stamps using laser technology.
Further, it is an object of the present invention to provide a means for manufacturing pre-inked stamps wherein the stamps may be cooled consistently throughout to a temperature at which laser technology may be used to accurately cut or etch the surface of the pad without allowing the ink to dissipate the heat generated by the laser.
Accordingly, it is also an object to provide such a means for manufacturing pre-inked stamps wherein the ink is cooled to a temperature which is not detrimental to the printing qualities of the ink when warmed to room temperature, or to a temperature at which the ink is to be applied.